Hi so you mean crop and image and add it to another image or your background?

Sounds like you want to make two new windows paste the image you want into one and start your new image as your background that you want it onto, ctrl + A to select all of the image you want to copy over then go over to the background image and ctrl + V to paste it in, I think that's what you wanted

You can copy your images from the web and paste them into blank documents, just right click the image and press copy and press paste on the photoshop document you have open or press ctrl + V. Alternatively you can save the images somewhere and open them up from Photoshop.

Ok this might be what you're wanting, if you just want to move the boy into another image, select you brush tool while in CS3, press Q button and then color in the boy with the red color the brush changes too. Then press Q again and it will make a selection, go to Select > Inverse and then press V to use your move tool and click and drag the boy onto another image, if you accidently got some of the background that wasn't part of what you wanted you can use the eraser tool to erase the parts you don't want on your new image.